Electric machines having a stator winding whose bar ends have brazed links or other connectors and which are insulated from one another and with respect to grounded housing parts are known in the art.
The bar ends of the stator winding of electric machines are generally insulated by means of a rigid oversized cap made of insulating material, which is pushed over the bar-to-bar connection. In the case of stator windings of large machines, these caps are filled, for example foam-filled or potted with a curing plastic. This has several drawbacks since it is always time-consuming to insulate the stator bar end because for this purpose the entire stator winding has to be brought into the correct position in each case. Moreover, relatively poor heat transfers ensue from the locally produced, thick layers of filling compound having a low thermal conductivity.
To overcome these drawbacks, various efforts have been made. For instance, the U.S. Pat. No. 5,729,068 discloses an electric machine having a stator winding which is impregnated by total immersion. The bar ends of the stator winding have soldering lugs, which are insulated from one another and with respect to, grounded housing parts. In order to simplify the assembly of the soldering lug insulation and at the same time to improve heat transfer, the soldering lugs are surrounded on all sides by a deformable insulating material, which is pervious as to impregnating resin. The insulating material is fixed by means of a shrinkable fabric, which is likewise pervious to the impregnating resin. The insulation and shrinkable fabric are impregnated and cured at the same time as the winding insulation.
The EP 0 077 665 B1 describes a tubular sleeve, for electrical insulation of an electrical conductor, the sleeve comprising interthreaded, fibrous yarns and an over coating which is coated onto and substantially covers and seals the exterior surface of that tubular sleeve, further to an electrical apparatus comprising at least one electrical conductor having a sleeve surrounding and intimately contacting said conductor.
Another effort to improve the known art is described in DE 42 37 079 A1. According to this disclosure, the blank ends of the conductor bars projecting from the end face of the lamination packet of the stator winding are coupled together to form the winding head. The blank ends of the conductor bars and the associated coupling conductors are provided with a fiber reinforced insulating cover, which is impregnated with a plastic resin.